The invention relates to a mechanical-magnetic connecting structure, i.e., a mechanical interlock supported by a magnetic force, which is suitable in particular for closures used on bags, backpacks and similar objects, wherein this recitation is not intended to limit the field of use of the invention.
Basically, such connecting structures can be divided into two main groups. There are mechanical connecting structures with opening and closure mechanisms made of a combination of mostly formfitting or force-transmitting elements. Frequently springs are used to maintain an interlocked state, so that closing and opening must be preformed against the spring force. Such connecting structures are known to a skilled artisan, so that reference will only be made to the state-of-the-art in subclasses IPC A44B.
Another main group of the connecting structures are magnetically operating connecting structures, where the magnetic force is used to hold the connection together. These connecting structures also sufficiently known to a skilled artisan for closures of bags and other containers, so that reference will here only be made to the state-of-the-art in subclasses IPC E05C.
Also known are combinations of these two main groups. In these combinations, it is typically attempted to satisfy specific requirements for a connecting structure through a suitable combination of the different properties of a mechanical connection and a magnetic connecting structure.
For a better understanding of the advantages of the invention, several major properties of the mechanical and magnetic pole connecting structures will now be explained.
A formfitting mechanical interlock has typically a mechanical component which is under tension, compression or shear when a load is applied to the interlock. The magnitude of the mechanical resistance of this component defines the stability of the connecting structure. Mechanical connecting structures can be produced cost-effectively, because very inexpensive steel parts or plastic parts can be employed for bag closures.
These mechanical connecting structures have essentially the property that a spring locking force must be exceeded when the components are plugged together. Handling of the connecting structure is therefore sometimes not very comfortable, so that magnetic connecting structures are substituted, because these attract each other automatically due to the magnetic force.
The force experienced during closing and opening is frequently referred to as haptic. In particular with manually operated closures, the haptic must be adapted to the force transmitted by the human hand.
With magnetic connections where the magnetic force is used directly to prevent the connection from opening, the magnet and the associated armature must be dimensioned commensurate with the holding force. These connections find practical application if no particular requirements are imposed on the holding force and the haptic.
However, in certain applications the closures must be oversized, for example when meeting certain safety requirements. This may be necessary, for example, for a backpack carried by mountain climbers. This backpack must not open even if many times the normal holding force is applied to the closure, which may occur, for example, during a fall. Closures with such a required characteristic are therefore constructed as mechanical closures because mechanical structures can have high safety factors without increased complexity or cost. These connecting structures therefore dominate the mass market.
Also known from the state-of-the-art are different mechanical connecting structures, wherein magnets are employed in addition to a mechanical interlock. However, these magnets are only used to hold the mechanical interlock together in the closed position. The magnetic force is here used instead of the spring force of a mechanical spring. This structure has an objectionable haptic. They can be closed relatively easily, but are more difficult to open.
No connecting structures are known in the art for the following requirements:                a. Locking is mechanical,        b. The connecting structure contracts automatically in the main loading direction,        c. The connecting structure can be easily opened, i.e., has a good haptic.        